1. Field of the Invention
The present invention relates to a cooling apparatus for an internal combustion engine provided with a thermostat device which is arranged in a circulation channel for circulating a coolant between the internal combustion engine (hereinafter also referred to as engine) of an automobile (for example) and a radiator and variably controls a temperature of the above-mentioned coolant.
2. Description of the Related Art
A thermostat device is provided with a thermoelement including therein a thermal expansion material which detects a temperature change of a coolant flowing through the inside of a circulation channel between an engine and a radiator to thereby expand and contract. A valve body is opened and closed by changes in volume due to the expansion and contraction of the thermal expansion material, serving a function to maintain the coolant at a predetermined temperature. Conventionally, various structures are known.
Further, an arrangement is proposed in which a thermostat assembly including the above-mentioned thermoelement is accommodated in a housing connected to the above-mentioned circulation channel and a temperature sensor for detecting the temperature of the coolant is provided in the above-mentioned housing. According to this arrangement, since the temperature of the coolant can be detected with the above-mentioned temperature sensor, the accuracy of the temperature control of the engine can be further improved using temperature information on the coolant.
As described above, the thermostat device in which the thermostat assembly and the temperature sensor are accommodated in one housing is disclosed in a prior art document, Japanese Patent Application Publication No. 2003-222264 (patent document 1).
Incidentally, according to the thermostat device disclosed in the above-mentioned prior art document, a support part (frame hook) of a spring support frame used for incorporating a thermoelement assembly into the housing serves as flow resistance, therefore there remains a problem of generating disorder and stagnation in the flow of the coolant.
Further, according to the apparatus disclosed in the above-mentioned prior art document, a temperature detecting tip of the temperature sensor is arranged near the frame hook which projects in the circulation hole of the above-mentioned housing, so that the temperature sensor measures a coolant temperature of a portion where disorder is generated in the flow of the coolant by the frame hook. Thus, it is not possible to raise the measurement accuracy of the coolant temperature, leaving room for improvement.
Furthermore, the temperature sensor provided for the above-mentioned thermostat device detects the coolant temperature (water temperature at outlet) from an engine coolant outlet, so as to be used for engine control, heater control, etc. However, in these days, the optimal temperature control of the coolant is required in terms of improving fuel consumption of the engine, and it is necessary to detect the coolant temperature at an engine coolant inflow part or around the thermostat which carries out the temperature control of the coolant.